It is known to provide pin-type synchronizer mechanisms which include means selectively operative to frictionally synchronize and then positive clutch first and second members to a third member, and which include blocker means for preventing the positive clutching during synchronization. It is also known to provide such synchronizer mechanisms for transmissions wherein the first member always rotates faster than the third member and the third member always rotates faster than the second member, and wherein the blocker means are continuously biased to a position for preventing the positive clutching. Such a synchronizer mechanism is disclosed in U.S. Pat. No. 3,221,851 and is incorporated herein by reference.
The synchronizer mechanism of the above-mentioned patent includes first and second friction and jaw clutch assemblies, a plurality of pins rigidly extending from a friction ring of each friction assembly and through openings in a radially extending shift flange, pre-energizer assemblies for engaging the friction assemblies in response to initial engaging movement of the flange, blockers defined by shoulders on the pins and about the flange openings for preventing asynchronous engagement of the jaw members.
It is also well known in the multiple ratio transmission art that synchronizer mechanisms may be used to reduce shift time of all or some of the transmission gear ratios. It is also known that the shift effort required by a vehicle operator, i.e., force applied to a shift lever, may be reduced by use of synchronizer mechanisms of the self-energizing type. Since operator shift effort generally increases with vehicle size and weight, synchronizer mechanisms of the self-energizing type are especially important for heavy duty trucks. Prior art examples of such mechanisms may be seen by reference to U.S. Pat. Nos. 2,410,511, 2,896,760, 3,548,983, 4,413,715, 4,836,348, and 4,869,353, which are incorporated herein by reference.
The synchronizer mechanisms of the above patents include friction and jaw members for respectively synchronizing and positive clutching a gear to a shaft; blockers engaged in response to a pre-energizer effecting initial engagement of the friction members in response to initial engaging movement of one of the jaw members by a shift force, the blockers being operative to prevent asynchronous engagement of the jaw members and to transmit the shift force to the friction members to increase synchronizing torque thereof; and self-energizing ramps reacting the torque to provide an additional force in the direction of and additive to the shift force for further increasing the synchronizing torque of the friction members.